False twisted yarn beam



1962 c. E. DANIELS ET AL 3,022,566

FALSE TWISTED YARN BEAM Filed Feb. 11, 1958 2 Sheets-Sheet 1 FIG I 5 s 1a e 72 W W 21 E1 0 I I '0 1. H fi [7 A a 2 '5 FIG. 2 I I6 1 1 18 n l6INVENTOR5 CHARLES WARD, NIELS NATHA NIEL NVER YETH ATTORNEY Feb. 27,1962 c. E. DANIELS ETAL 3,022,566

FALSE TWISTED YARN BEAM 2 Sheets-Sheet 2 Filed Feb. 11, 1958 FIGS? FIG.

FIG. IO

83 R L O E m WD D m M E S E L R A H C NATHANIEL CONVERS WYETH ATTORNEYUnited States Patent 3,022,566 FALSE TWKSTED YARN BEAM Charles EdwardDaniels, Wilmington, and Nathaniel Convers Wyeth, Hockessin, Del.,assignors to E. I. du

Pont de Nemours and Company, Wilmington, DeL, a

corporation of Delaware Filed Feb. 11, 1958, Ser. No. 714,549 6 Claims.(Cl. 28-78) This invention relates to yarn winding and packaging, andhas particular reference to beaming continuous multifilament Zero-twistyarn. More specifically, this inven tion relates to a novel and usefulprocess for continuously twisting such yarn during beaming, and to thenovel beam package produced thereby.

Yarn, thread, fibers, and the like filamentary structures areconveniently packaged and transported on beams. Such beams are preparedby simultaneously winding with slight traversing a plurality of yarnends maintained in a spaced, parallel, coplanar relationship, i.e., as awarp sheet onto a beam, a single large core or a yarn package supportprovided with suitable end flanges. Beams ordinarily may contain on theorder of one hundred or more yarn ends, and upwards to many hundreds ofpounds of yarn. A beam may be used by the consumer as received toprovide the warp for weaving (loom beam) or as a single supply packagefor large-scale twisting, plying, and the like textile operations(supply beam). In either case, the use of the beam enables the handlingand transporting of large quantities of yarn with but a minimum ofsingleend operations.

Yarn is wound onto a beam at essentially Zero helix angle since thetraverse stroke during beaming normally is no greater than theyarn-to-yarn spacing in the warp eing beamed. To insure that individualfilaments in the yarn bundles do not become trapped, entangled, orbroken due to overlap with the filaments of adjacent or subsequentlywound yarn, i.e., to insure that the yarn can be unwound (backwound)from the beam, it is necessary to apply 'a certain amount of twist tothe individual yarn ends prior to beaming. This producer twist isrequired in order to maintain the unity of the yarn bundle, and isapplied at relatively low levels (nominally about 0.5 turn per inch) ascompared to consumer twist, which may range upwards to several turns perinch. Yarn containing such producer twist does not form the so-calledfilament ringers (filament wraps on the beam) because any potentialtrapped or tangled filaments are broken and pulled along by the parentyarn during backwinding. However, without such twist, breaks which occurduring backwinding lead to the formation of ringers, which, in turn,cause considerable yarn waste and may lead to the eventual interruptionof the backwinding operation. Therefore, it is required in every beamingoperation that the individual yarn ends be twisted or receive anequivalent treatment prior to beaming, not to facilitate preparation ofthe beam, which is no problem, but to permit the yarn to be backwoundtherefrom, which indeed is a real problem.

Although twisting insures the formation of a backwindable beam, suchtwisting has involved much additional yarn handling, and is costly interms of time and equipment required. Moreover, the mechanics oftwisting and the additional handling often result in lower yarn quality.Finally, since the consumers twist demands vary widely depending uponthe end use of the yarn, and since the presence of the costly initialproducer twist in the yarn may render such subsequent twistingnonuniform, thereby affecting the fatigue and load-carrying ability ofthe yarn, there has been a need for means to beam yarn without priortwisting (i.e., means which would permit beaming zero-twist or as-spunyarn directly into a backwind- "ice able package). By zero-twist yarn ismeant yarn having no substantial process twist, excluding theomnipresent slight twist in the yarn resulting from normal handling(e.g., twist resulting when removing yarn from a stationary package)which for all practical purposes is negligible. Despite the need,however, no satisfactory method for preparing backwindable beams ofzero-twist yarn is known to the art.

That the problem of beaming zero-twist yarn has been recognized is shownby Bradshaw (US. 2,224,665), who

discloses that slashing (sizing) such yarn prior to beaming results in abackwindable beam. The slashing, in this case, serves in a mannersimilar to twisting, by binding the separate filaments of the yarn intoa coherent bundle. However, the slashing operation may entail as muchadditional handling and equipment as does twisting, is timeconsuming,and requires that the sized yarn be rigorously dried prior to beaming,since otherwise the yarn bundles stick together. Further, the size onthe yarn often must be removed at some subsequent stage of handling bythe consumer. Karns (US. 2,324,584), seeking to avoid the need foreither twisting or slashing, proposed to traverse a single thread alongthe length of the beam so as to separate the successive windings on thebeam. During backwinding, the traverse thread serves to break outtrapped and tangled filaments, thereby avoiding the formation ofringers.

ing and subsequent handling, which is the crux of the problem of beamingZero-twist yarn. Moreover, the breaking-out process often leads to yarnof unacceptable quality containing an excessive number of brokenfilamerits.

Recently, the problem of. beaming zero-twist yarn has arisen anew.Technological advances in the textile art have led to improved andhigher speed production of yarn, requiring rapid, continuous yarnpackaging opera tions. For example, many benefits derive from spinningand drawing nylon yarn in a coupled operation, prior to initialpackaging. It would be highly desirableto beam directly from such aspinning package, without having to divert the yarn to a twisting orslashing operation. Recent advances in apparatus design have made spinbeaming (i.e., packaging yarn on a beam immediately as it is formed) afeasible operation save for the need for twisting. It is apparent thatmany improvements in the con tinuous production of yarn would derivefrom a suitable process for beaming zero-twist yarn, and would enablebeaming much of the current zero-twist yarn production presently beingsold on single-end packages.

One object of this invention is to provide a backwind able beam woundfrom a warp of continuous multifilament yarn, the separate yarn endshaving substantiall zero net twist therein.

A further object is a process for beaming continuous muitifilarnent yarnhaving substantially zero net twist therein, the beam so produced beingbackwindable with: out incurring tangled or trapped filaments, andwithout the formation of filament ringers.

A still further object is a backwinda'ble beam of a warp of continuousmultifilament yarn, the separate yarn ends having a periodic, reversing,i.e., alternating (false) twist preferably throughout theentire length.

Yet another object is a process for backwinding from a beam to supply awarp of continuous multifilarnent yarn, the separate yarn ends havingsubstantially zero net.

twist therein. These and other objects, together with means foraccomplishing these objects, will appear hereinafter.

The objects of this invention are accomplished in general bycontinuously subjecting individual ends of a warp of continuousmultifilarnent zero-twist yarn to the However, Karns method does noteliminate trapped and tangled filaments during package 3 action of afalse twister, imparting thereto'a periodically reversing (i.e.,alternating twist) of average twist level of at least about 0.4 turn perinch, and immediately thereafter winding such a warp onto abeam. in theusual manner and at usual beaming speeds. In a preferred embodiment,individual zero-twis't'yarns of a warp are subjected to intermittentpneumatic unidirectional twisting with air so as topro'duce a warpwith'indiv'idual ends having from about 0.4 to'qabout. 0.8 average turnper inch of alternating twist at a period length of from about 4 toabout 16 feet while winding at a yarn tension of from about 30 to about60 grams. There results a novel and useful loom or supply beamcontaining'a warp of yarn,

the individual ends of which have substantially zero net twist, whichmay be backwound with either removal or retention of the alternatingtwist applied thereto by the process of the present invention. Such abeam may be backwound without incurring tangled or trapped yarnfilaments, and without the formation of objectionable filament ringers.

The'invention will be more clearly understood by rcference to theattached drawings.

7 FIGURE 1 shows a schematic view of an apparatus useful in the practiceof the present invention.

FIGURE 2 shows in schematic section an apparatus useful for twistingyarn pneumatically.

FIGURE 3' shows an end view of the apparatus of FIGURE 2.

FIGURE 4 shows an enlarged, schematic partial section of the apparatusofFIGURE 2 taken alongthe sertion line aaf.

FIGURES- shows a sectional viewof several pneumatic twisters togetherwith fluid supply means suitably ar ranged for use in beaming. FIGURE 54shows a fluid supply regulator useful with the apparatus of FIGURE 5.FIGURE, 6 shows a side elevation of one apparatus useful for twistingyarn mechanically. 7

FIGURE 7 shows a left-end view of the; apparatus of FIGURE 6,

FIGURE 8 is a sectional view of another apparatus useful for twistingyarn mechanically.

FIGURE 9 shows a left-end view (rotated 90 counterclockwise) of theapparatus of FIGURE 8. I

FIGURES 10 and 11. show in enlarged schematic section other pneumatictwisters suitable for use in the present invention.

"FIGURE 12 shows graphically the lengthwise variation in twist along thelengthof a segment of yarn prepared in accordance with this invention.

Referring to FIGURE 1, there is shownschematically a' conventional;beaming apparatus modified to include false twisting means for carryingout the process of the instantv invention. In operation, a plurality of.yarn. ends indicated at 1 (from a source not shown): is led over theguide 2, which1may be a pinboard, an eyelet board, or other suitableguiding means. At. this point, the individual, yarn ends. are combinedat form a warp sheet. The. warp sheet is passed. about vibration controland delivery rolls at 3 andv then through separator guide (a pin board,comb, grooved rolls,.-or the like), eyelet guide 6, then twisting means8 where each yarn is false a twisted. Downstream'from the twisterStheyarns pass through an eyeletguide 7. Eyelet guides 6 and 7 are'rnounted on eyelet boards located approximately the same distanceupstream anddownstream, respectively, from thetwister 8, and servetocenterlthe yarn in the twister and'to control lateral fluctuations ofthe individual yarns in the warp sheet. The twisted yarns then encountertraverse comb 9 and are thereby traversed over idler roll and onto beam11, the lay of the warp being controlled by the presser roll 15. Beam 11is ofv conventional design, having a barrel portion 12 and a flange 13mounted at either extremity to control and contain the yarn bulldup,indicated at 14. Excluding the twisttermed hereinafterequilibriumtwisting.

URE l is conventional and individual components may be altered, added,or even removed, inaccordance with accepted beaming practice. The yarnsupply means (not shown) may be packages mounted in a conventionalcreel, or may consist of a number of spinning machines, whereby as-spunyarn is forwarded directly to the beam without intervening discontinuousprocess steps.

Utilizing the apparatus of FIGURE 1, the yarn 1 passing from the supplymeans'to beam 11 is false twisted, that is, twisted in oppositedirections upstream and downstream from the twister. 'Downstream twistis trapped on the beam while upstream twist of equal amount but oppositedirection is accumulated. If such twisting continues, the point israpidly reached where the upstream twist is accumulated to an extentsufficient to counteract the twisting torque of the twister, resultingin either the winding of Zero-twist yarn onto the beam or completebreakdown of the yarn line. Such a condition will be In order that theupstream twist may reach the beam, the torque of the twister must berelieved or otherwise overcome. Three important methods are availablefor permitting the periodic alternation of twist in the yarn beingpackaged and which avoid the condition of equilibrium twisting.

The simplest method of applying periodically alternating twist to arunning yarn line according to this invention comprises intermittentapplication of twisting. Thus, after the upstream twist has, accumulatedto a predetermined extent, the twister torque may be reduced oreliminated to allow some or all of the accumulated upstream twist topass downstream and onto the beam. Suchan intermittent twist-no-twistaction, when suitably timed with respectto yarn speed permits the winching and packaging of yarn having good uniformity of twist period andlevel, with dwell at twist reversal points (i.e., points ofzero twist)being at aminirnum. The intermittent application (pulsating) ofunidirectional twist is preferred for the purposes of the presentinvention.

Periodically alternating twist may also be applied to a running'yarnline according to this invention by intermittently applying twisting inopposite directions. Such a method is more desirable, however, becauseless sensitive to timing of the twist cycles. These two methods areapplicable to either mechanical or pneumatic twisting. When. employingpneumatic twisting, periodically. alternating twist may be applied toarunning yarn line with constant unidirectional application of twistingbyfperiodically varying the tension in the yarn. After upstream twisthas accumulated to the desired extent, the tension on the yarn line isincreased, thereby permitting some ofthe upstream twist to: pass throughthe twister and downstream onto the beam. The efiectiveness of this anduniformity of the product so produced;

FIGURE 12 shows graphically the lengthwise variation in twist along thelength of a segment of yarn twisted in accordance withthisinventiomwherein ordinate 05 indicates level of S twist and ordinate02. indicates level a of .the Z twist at any point along the yarnlength, i.e.,

the abscissaoL. At the initiation of twisting (at 0), the S twist levelrises rapidly'to a maximum a, then, approaching equilibrium twisting,falls off towards b. Twisting is stopped or reversed at b, allowing theup stream accumulation of twist to pass downstreamand onto the beam.Such practice results in Z twist rising to its maximum twist level at c,then, again approaching equilibrium twisting, falling off towards d, atwhich point twisting in the 8 direction is initated, and the processcommencng at o is repeated. By suitable variation of processingconditions, the curve of FIGURE 12 can be made to assume a variety ofproportions, and, of course, need not be symmetrical.

FIGURES 2 and 3 show section and end views respectively of arepresentative pneumatic twister suitable for use in this invention.This twisting means comprises cylindrical yarn passageway 1618, withenlarged exhaust section 16, beveled section 17, and twisting section18, the latter being tangentially intercepted by the fluid conduit 19 ina plane normal to the axis of the yarn passageway. In operation, fluidpassing through conduit 19 intercepts the yarn 1 in twisting section 13and imparts thereto a crank twisting action. The path of the highvelocity twisting fluid in the twister is indicated by arrows in FIGURE4. By periodically interrupting the supply of the fluid to the twister,intermittent unidirectional application of twist described in the foregoing is achieved. With reference to FIGURE 12, fluid is supplied to thetwister during passage of a segment of yarn having length o-b. Fluidsupply is interrupted for a yarn length bd. Enlarged exhaust section 16of the twister 3 serves to facilitate the release of exhaust twistingfluid with minimum interaction with the yarn. Beveled section 17 servesto guide the yarn into twisting section 18, and serves to minimize yarndamage. The length of yarn twisting section 18 should not be less thanits diameter, and preferably, the total length of the yarn passagewaywill be about six times its diameter for optimum twisting. Further, theratio of the area or" the yarn twisting-section 18 to the area of thefluid conduit 19 may vary from about 4:1 to about :1, but is preferably6:1. Ratio of the diameter of the yarn to the diameter of the twistingsection 18should be from about 1:2 to about 1:10, and is preferablyabout 1:4. The yarn twist-section 18 and the fluid conduit 19 arepreferably cylindrical in shape, as shown, but either or both may beother than circular in cross section and neither need be uniform in areaor cross-sectional form throughout its length. It is readily apparentthat many variations of the twister from the representation shown inFIGURE 2 are possible.

Air at room temperature is a suitable fluid for twisting yarn inaccordance with the preferred practice of this invention. However, otherfluids or liquids substantially inert to the yarn, such as carbondioxide, nitrogen and the like may be utilized if desirable, and suchfluid may be heated or refrigerated as desired, so long as such atemperature is not deleterious to the yarn being twisted. Air is thepreferred twisting fluid, and will be referred to herein forillustrative purposes as representative of all such twisting fluids.Steam may also be employed.

In FIGURE 5, an arrangement is shown whereby several pneumatic twistersare employed in a side-by-side relationship for use in beaming inaccordance with PIG- URE 1. FIGURE 5 shows several twisters 18 mountedin a single block 8, which is securely attached to the manifold means21. Manifold means 21 contains an enlarged fluid supply pipe from whicha plurality of fluid ducts 22 communicate with the fluid conduit 19 ofeach twister. If desired, either or both the fluid duct 22 and the fluidconduit 19 may be outwardly beveled at eir respective points of contactto facilitate alignment. in operation, fluid from an external source(not shown) is supplied at either or both ends of the fluid supply pipe6 constant source of fluid by utilizing the apparatus of FIGURE 5a,which consists of a tubular valve means 20a adapted to be rotatablymounted in the fluid supply pipe 29 of FIGURE 5 so that each of theopenings 22a may rotate into alignment with the corresponding fluidducts 22 in manifold 21. Openings 22a are cut about half of the wayaround the circumference of the tubular valve means 20a, and are ofabout the same or slightly greater width than the diameter of the fluidduct 22. In operation, the tubular valve means 2% is caused to rotate ata predetermined rate in the fluid supply pipe 20 of the manifold 21.Fluid from a constant source is supplied at either or both ends of thetubular valve 29a. When an opening 22a of the tubular valve Zita rotatesinto an open position with respect to the corresponding fluid conduit22, fluid passes through the said duct 22 and the conduit 19, therebytwisting the yarn passing thorugh the twister 18. Fluid is suppliedduring about one-half of each cycle of rotation to each twister, hencetwist alternation is controlled and maintained uniform. Since thetwisting or open cycle of each opening 22a partically overlaps that ofan adjacent opening, fluid is consumed at a constant rate duringoperation. Otherwise, if all twisters operate simultaneously, thereexists the possibility of insufficient supply of fluid to those twisterslocated farthest from the source of supply. However, where an adequatesupply of fluid is assured, all twisters may be operated simultaneouslywith equal eflicacy. 'It is obvious that the individual twisters may beoperated in or out-of phase with respect to adjacent twisters and thatthey'may even twist in opposite directions. 7 Many varieties ofmanii'olding may also be employed. For large-scale twisting operations,involving a large number of individual twisting elements, it is oftenpreferred to employ several blocks of twisters, rather than a singleblock carrying all of the twisters. In any such apparatus, twist leveland uniformity across the warp sheet is dependent on and requires anadequate and reasonably constant supply of fluid. Fluid supply should besuitably synchronized with the beamer so that twisting ceases when thebeaming is stopped for any reason.

Twisting in accordance with this invention, whether it be intermittentunidirectional or alternately in opposite directions, leads to yarnhaving segments of twist in one direction, each positioned between twosegments 'containing the opposite twist. All segments will usuallycontain about the same length of yarn, and about the same amount ofabsolute twist. The net twist in the yarn is essentially zero, that is,the total -8 twist'is equal to the total Z twist. The resulting yarn iscalled an alternating twist yarn.

The parameters used to define such an alternating twist yarn are thetwist period, maximum twist, and average twist. Twist period or cyclelength is the distance along the threadline that contains completesections of both S and Z twist. A length of yarn containing twist in butone direction (8 or Z) is described as the increment length of twist.The average twist level is defined as the absolute numerical average oftwist per unit length, taken over a representative sample length of yarn(several twist periods), regardless of twist direction. Maximum twist isthe largest amount of twist (in turns per inch) encountered in an S or Ztwist section. The three parameters are interrelated by the generalitythat maximum twist approaches the average twist value as periodincreases, i.e., the curve of FIGURE 12 tends to flatten at longerperiods. In FIGURE 12, the twist period is the length of segment 0d;increment level of twist is the length of segments ob and bd; maximumtwist is indicated at a or c, and average twist is given by dotted lineoL'.

Yarn may also be twisted in accordance with this invention by utilizingmechanical means. In FIGURES 6-7 are shown mechanical twister 23 mountedin reversibly driven rotating sleeve 25, and having machined thereinhelical yarn guide 24 adapted to receive a yarn end and characterized byhaving yarn entry and exit sections located coaxially with respect totwister 23 but axially displaced therebetween. In operation, yarnpassing through the rotating twisters enters the helical guide, is

versing the direction of rotation of sleeve 25. This may be accomplishedby positioning the twister assembly betweentwo belts being driven inopposite directions, and by suitably shifting the twister assembly sothat it is alternately being driven by the one belt and then the other.Surprisingly, such practice permits rapid twist reversal and minimumreversal dwell even at operating speeds up to about 20,000-r.p.m.

An alternate mechanical twister suitable for use in the presentinvention is seen in FIGURES 8-9, wherein are shown views of a twisterconsisting of fixed member 26 and shifting member 27, both mountedcoaxially within driven cylindrical sleeve 28. Members 26 and .27 eachcontain a portion of yarn passageway 29 which may contain suitablebushings to resist abrasion by the running yarn and at the same timeprotectthe yarn from damage. Each of members 26 and 27 contained roundedrectangu- .lar slots 31a and 315, respectively, which cooperate inserving as a guide for pin 32. The apparatus is shown with pin32 in thedisengaged position with respect to yarn 1. Pin 32 can be shifted intothe yarn line by urging'shifting member 27 into fixed member 26 (moving27 to the right). Such shifting causes pin 32 to move from position- Ato position B in FIGURE 9. In operation, the entire twister assemblyrotates unidirectionafly by, e.g., a belt drive frictionallycontactingsleeve 28. The shifting member 27 is periodically shifted into fixedmember 26, causing yarn being alternately twisted (pin 32 engaging =yarnline) and being allowed to pass the twister without twisting (pin 32.inthe disengaged position), i.e., permitting. the

upstreamaccumulation of twist to pass downstream and onto the beam.Shifting'member 27 is conveniently level is the most important of thethree in this invention. in that its value determines theback-windability of. the

beam. An average twist level of at least about 0.4 turn per inch hasbeen found critical in the practice of'this invention. Below that value,twist periodicity becomes difiicult to control, andjfilarnent ringersappear on the beam during back winding. Where it is desirable that twistbe completely removed during backwinding less than about 0.8 turn perinch average twist has been found to be desirable since otherwise twistremoval may be incomplete, leading to twist variation in theconsumer-twisted product. Such variable twist may affect the fatigue andload-bearing properties of the yarn, especially in the case of supplybeams of yarn to be used in' industrial applications (e.g., tire cord).The optimum and hence preferred average twist level is about 0.6 turnper inch, which permits most efficient. backwinding with substantiallycomplete twist removal. Where twist is to be retained duringbackwinding, as in a loom beam, average twist level may range upwards to30 turns per inch or more, as desired. Such high levels of twist arequite practical using any one of several species of pneumatic twisters,which are capable of twisting at rates in excess of one millionrevolutions per minute. capable of imparting more than 66 turns of twistper inch at yarn speeds of 500 yards per minute, at normal oper-- atingefiiciency.

The value of the twist period? also governs to an appreciable extent theoperability of the beam during backwinding as well as the extent ofretentionor removal of. Accordingly, the twist period should be suchthat twist. twist is accumulated in the yarn being wound during beaming,but so that it either may be removedtor retained during backwinding.

In operations wherein complete removal of twist during backwinding isdesired, a twist period of from about 4 evident that twist cancellationor removal occurs when spring-loaded and thereby; maybe directly shiftedby use of a cam of suitable profile. The pin'32 should be com-' posed ofa material capable of resisting" the wear induced by repeated shiftingand contact with the running yarn,

but, of course, such compositions should not abrade the yarn. Severalsuch twister assemblies may be located within a single driven belt, andpreferably are positioned in a staggered relationshipwith respect to oneanother to. provide ,warp twisting. at the usual yarn-to-yarn spacing.Such considerations also apply to the helical guide to the absence ofmoving or rotating parts and minimum yarn contact-(no yarndegradation)is practically insta11-- taneous in its action, and is very economicflto operate. Moreover, such twisters are readily adaptable tooperate onextremely close centers, as required in warp twisting. and when the"twister conforms to the operable and/or preferreddimensions asindicated hereinabove, uniform and reproducible twisting is obtained. 7

The parameters most usefulin describing the alternating twist in theindividual yarn ends in the warp, as wound on the beam, are the twistperiod, the average level of twist{ and the maximum level of twist.Average twist ever sections of yarn having segments of twist in oppositedirections are freely suspended. In operations wherein retention oftwist is desired, longer periods may be employed to advantage.Accordingly, at a given rate of twisting, an increase in the twistperiod causes the twist distribution curve of FIGURE 12 to flatten,which results in a proportionate increase in the length of the reversalsections, i.e., segments on the said curve having effectively zerotwist. If such regions are permitted to become overly extended, theabove-mentioned difliculties common to zero-twist yarn'may beencountered. In view of these potential difiiculties, it is desirableto'avoid extremes in period length, or, alternatively, increasetheaverage level of twist. Another equally suitable procedure which.avoids the problem of extended reversal points is outof phase. twisting,such as results from utilizing the fluid supply regulator of FIGURE 5a,which assures that the yarn windings will not have their respectivereversal points wound adjacent to one another.

When utilizing a mechanical twister in the process of thisinvention, theaverage twistlevel imparted to the running yarn line is astraightforward function of the rate of twister rotation since suchdevices are. relatively insensitive to yarntension, and incursubstantially no slippage given yarn, the average level of alternatingtwist imparted to the yarn line depends on three factors: yarn speed,yarn For example, the twister of FIGURE 2 is When utilizing any givenpneumat1c twister (fixed dimensions), and'when twisting any tension, andrate of twisting, which, for the sake of the present discussion may beexpressed in terms of fluid supply, e.g., air pressure. When twisting atconstant cycle timing and air supply, the yarn speed, of course,determines the length of the segment of yarn over which twist is appliedduring any given twist cycle, and hence determines the average twistlevel. The yarn tension also governs the average twist level, since theyarn must be axially displaced before twisting is initiated. Byincreasing the tension on the yarn line, such displacement is resisted.Finally, the air pressure applied to the twister determines the rate oftwisting and, therefore, the average level of alternating twist in anygiven segment of yarn during the twist cycle.

Tension and air pressure are interdependent variables, i.e., an increasein one decreases the effect of the other, and conversely. At constanttension, the relationship between average twist level, expressed interms of turns per unit length, with respect to air pressure applied tothe twister is substantially linear, hence to increase the average twistlevel, all other factors being the same, an increase in air pressure issufiicient.

For either mechanical or pneumatic twisting, the twist period dependsmainly upon the duration of twisting. By duration of twisting is meantthe twisting relationship which exists during any one twisting cycle,and which is related to the yarn speed and the time of twisting duringthe twisting cycle, i.e., the time interval during which the twister istwisting in a given direction. Thus, the duration of twisting determinesthe length of the yarn segment over which twist of a given direction isaccumulated, and hence also determines the twist period except duringconditions of equilibrium twisting. During equilibrium twisting, ofcourse, zero-twist yarn is packaged. To avoid packaging g zero-twistyarn, the cycle during which the twister operates (in intermittentunidirectional twisting) should be adjusted to less than that requiredto establish an equilibrium twisting condition. Although there exists notheoretical upper limit for the twist period, there is a practical upperlimit, which is determined by the distance between the twister and thefirst upstream snubbing guide. A snubbing guide tends to inhibit thefurther upstream accumulation of twist. Therefore, twist is confined tothe yarn segment between such a snubbing guide and the twister, andsince only a certain amount of twist may be accumulated before theupstream twist counter torque becomes equal to the applied twistertorque (at initiation of equilibrium twisting), the upper limit of theperiod is limited.

The nature of the process of this invention makes certain demands uponthe associated beaming equipment. As mentioned, an alternating twist istrapped or conlined by a snubbing-type guide, e.g., pinch rolls, niprolls, and the like. Twist ordinarily cannot pass either upstream ordownstream from such a guide, certainly not in a continuous manner asrequired for the present purposes. That twist which does pass such asnubbing guide does so in an uncontrolled and intermittent fashion, andat rather high levels which are subsequently distributed over longlengths of zero-twist yarn, and are thereby rendered ineffectual.Accordingly, such guides as the yarn may encounter in the vicinity ofthe twister, and particularly downstream therefrom should be of thenon-snubbing variety, such as eyelet guides, comb guides, and freelyrotating idler rolls. The roll 19 in FIGURE 1 is of such freely rotatingoperation. Upstream from the twister, the location of the first snubbingguide determines the maximum twist period. Referring to FIGURE 1, thevibration control and delivery rolls 3 serve in that capacity. V

The alternate twist yarn of this invention may be backwound in such amanner as to remove or retain twist, as required by the consumer. In thecase of supply beams, e.g., to be used in the preparation or" tire cord,substantially complete twist removal is usually desirable. In

the case of a loom or warp beam, the presence of a certain amount ofresidual twist may be highly desirable, or in some cases required.Accordingly, the wound-yarn parameters of average twist level and twistperiod should be adjusted, keeping in mind the possible end uses.

Twist is removed during backwinding by either of two methods. Twist isremoved if the free suspended length of yarn during backwinding or anysubsequent textile operation is allowed to achieve or exceed the twistperiod. By free suspended length is meant the length of running yarntensioned between two suubbing-type guides, e.g., between the packageand a snubbiug guide. If shorter portions of the yarn are freelysuspended, twist removal is incomplete, e.g., about half of thealternating twist is removed when an increment length of yarn is freelysuspended. The relationship between twist removal and suspended lengthis, for all practical purposes, a linear one. In addition, since twistis contained by snubbing guides, as indicated earlier, when such a guideis encountered during backwinding, twist will tend to accumulate and beconcentrated upstream from such a guide. Twist of the opposite directionwill also be trapped, hence twist cancellation then occurs. Accordingly,by suitable positioning of snubbing guides with respect to the beamduring backwinding, twist removal may be accomplished. It is evidentthat in either method of twist removal, some twist may be retained. Yetfor every section of twist that is not removed, there will subsequentlyoccur passage of the twist of the opposite direction, leading toeventual complete twist cancellation. in either method of removingtwist, the completeness and efiiciency of such twist removal is enhancedby utilizing increased yarn tensions during backwinding.

if it is desirable that twist be retained during backwinding, it isobvious that both of the above-mentioned conditions are to be avoided.Therefore, to retain twist during backwinding or any subsequent textileoperation, the free suspended length of yarn should be kept as low aspossible, and the use of snubbing guides or the like means avoided. Theretention of twist may be further assurred by utilizing a higher averagetwist level initially, or by increasing the period, or both. Twist mayalso be set" by twisting the yarn in the plastic state (via heat orresidual solvent), followed by cooling or by slashing the as-twistedyarn. The most desirable method to insure residual twist retention is toincrease the average twist level. This is accomplished in pneumatictwisting by increasing the air flow. Increasing the average twist levelis preferred over increasing the period, since by the latter method thereversal length between segments containing twist in opposite directionsincreases. Such exaggerated sections of yarn having little or no twistare subject to the same difficulties during backwinding as is zero-twistyarn. It is preferred, therefore, that the over-all twist period beabout from 4 to 16 feet in order to minimize segments having zero twistin the separate yarns in the warp.

One of the most important process variables effecting the practice ofthe present invention is yarn tension. Suiiicient tension is requiredduring winding to maintain the stability and spacing of the separateyarn ends in the warp Sheet, and to insure acceptable package formationon the beam. However, excessive tension inhibits the effect of action ofthe pneumatic twister, and insufficient tension permits rolling togetherof adjacent yarn lines, due at least in part to the upstream anddownstream flutter induced by the exhaust gases from the twister.Moreover, it is required that the tension be uniform across the warp,which is partly controlled by the diametrical uniformity of thevibration control and delivery rolls indicated at 3 and of the idlerroll 10 in FIGURE 1. The yarn line tension should be suflicient toinsure that the yarn is reasonably centered in the pneumatic twisterduring winding and twisting. Accordingly, it is preferred that yarntensions from about 30 grams to about 60 Tenn.) eyelets.

' may be necessary in the case of beaming at very close yarn-to-yarnspacing in the warp. The present considerations apply to warp spacingsof about one-fourth to onehalf of an inch. Tension values are reportedat the beam unless otherwise indicated. The yarn suppliedfrom the creelis usually at about 30 'to 45 grams tension. The vibrationcontrol-delivery roll system (indicated at 3,

FIGURE 1) adds about 5 grams tension, hence the upstream yarn tension isabout 35 to 50 grams, which results in yarn being'supplied from thetwister to the beam at about 45-60 grams tension. It is preferred thatthe minimum values of tension within these ranges be em ployed whereverpossible, consistent with warp and yarnline stability.

' In the preparation of warp or loom beams, it is usually preferred thatsuch beams be prepared via section beams, as is well known in the artofpackaging and winding. Thus, several section beams containing 500 ormore yarn ends can be used to prepare warp beams containing severalthousand individual yarn ends. Of course, when using the apparatus ofthis invention to prepare beams at very close yarn-to-yarn spacings inthe warp, i.e., at high end densities, blocks of twisters may bedisposed in a horizontal and vertical staggered array, permitting twisting of a 'very large number'of ends without requiring an unduly large orbulky apparatus. Bythis procedure, a warp containing or more ends perinch is easily beamed according to the instant invention. 7

The process of this invention is illustrated by the following examples.

EXAMPLE 1 The process of this invention is carried out utilizing theapparatus of FIGURE 1 '(Cocker Beamer Model SD-49,-supplied by CookerMachine and Foundry Co.,

Such measurements are averaged without regard to direction of twist.These measurements are precise to about 0.05 turn per inch (t.p.i.). Theperiod length is determined by actual measurement of the distancebetween points of twist reversal in the yarn immediately as removedfrom' the beam. The results of these determinations are summarized inTable I.

The results of these tests show the linear relationship between airpressure (fluid supply) and. average twist level, and the criticaldependence of operability on the average twist level. About 0.4 t.p.i.of average alternatnig twist is necessary to prepare'a backwindablebeam. Referring to the curve of FIGURE 12, the yarn from Test AD has aperiod length of 6 feet (0d), maximum 8 twist (twister on) of about 0.9t.p.i. (a), maximum 2 "twist (twister ofi) of about 0.82 t.p.i. .(c),and su Gastonia, NC.) equipped with the pneumatic twister of FIGURES2-3arranged in 16 blocks, 11 twisters per block, according to FIGURE 5.The dimensions ofthe individual twisters are as follows:

Length Diameter,

inches Exhaust section 16 0.24 inch each.-. Beveled section 17 60 bevelTwister section 18 Fuid (air) conduit 19 Tot 0.875 inch 'The upstreamguide 6 and the downstream guide ,7 are both located about 6 inches fromthe twister block, and contain Al Si Mag (American Lava Corp,Chattanooga, The twister operates on an on-ofi cycle, i.e., by theintermittent application of unidirectional twist. Each complete cycle isof the same duration, about 4.1 cycles/second, hence twisting isefiected for periods of 0.12 second duration. Since the yarn speed is500 y.p.m., such a twisting cycle determines a period length of about 6feet. The twisted yarn :ends in 'the warp sheet are traversed onto thebeam at grams tension, the traverse stroke being about 4521116111. AfterV winding, the beam is backwound. During backwinding, the average levelof twist is determined, the periodicity checked, and the behavior(operability) during backwinding is noted. The average level of twist isdetermined by measuring the twist contained a in 24 successive 6-inchlengths of yarn immediately as removed from the beam.

stantially no dwell at the reversal point b. Air is supplied to thetwister from o to b, and is cut off from b to d, i.e., the twistingcycle is adjusted to change precisely at the point of initiation ofequilibrium twisting, thereby avoiding that condition. When the twistingcycle time is increased, there results sections of yarn having zerotwist between the segments of yarn containing twist, i.e., there resultsexaggerated twist reversal points. When the twisting cycle time isreduced, the curve of FIGURE 12 assumes a saw toot contour.

EXAMFLE 2 The mechanical twister of FIGURES 76-7 is utilized with theapparatus of FIGURE 1 to beam 176 ends of 840 denier, filamentpoly(hexamethylene adipamide) yarn, supplied from a creel at 35-40 gramstension. The twisters are positioned between two belts driven inopposite directions. During contact with either belt, the twisterrotates at l8,000 revolutions per minute (r.p.m.). The twister contactseither belt for 0.25 second, then is immediately shifted to the otherbelt for the same contact time. Theyarn isbeamed at 500 y.p.m., hencethe twist period is about 12 feet, at an average level of twist or" 0.5t.p.i. Such a beam is fully operable during backwinding, twistperiodicity is uniform, andsubstantially no filament ringers are formed.

EXAMPLE 3 Beams prepared according to Examples 1, 2, or 3 are backwoundto supply conventional downtwisting apparatus. Each yarn end is passedfrom the beam via guide means through drop-type tension rolls servingeach twisting position, thence to the ring and associated traveler andonto a conventional twister package (pirn) mounted The beam so preparedis on a rotating spindle. The shortest beam-to-tension roll (a form ofsnubbing guide) distance is about feet. Twist removal is substantiallycomplete up to about 0.6 t.p.i., above which, however, twist removalbecomes progressively less complete, as evidenced by twist variation inthe downtwisted product. For example, when the average residual twist inthe yarn is about 0.2 t.p.i. of alternating twist, the net twistvariation in the downtwisted product is at once about 0.4 t.p.i., whichoccurs in addition to the twist variability which normally occurs in thedowntwister package (pirn). Such twist variation is highly detrimentalto the performance characteristics of the yarn in demanding industrialapplications, e.g., in tire cord. However, by increasing the averagetwist level to above about 0.8 t.p.i., some twist retention occurs.Retention of twist may be highly desirable in many applications, e.g.,in textile uses. Progressively more twist retention occurs as theaverage twist level is further increased.

The process of this invention has been illustrated by intermittentunidirectional twisting (Examples 1 and 3) and intermittenttwo-directional twisting (Example 2). Though less desirable, it is alsopossible to apply an alternating twist to a running yarn line with theapplication of unidirectional twisting by periodically varying the yarntension, speed, the twister speed, or the upstream guide distance.Moreover, such twisting may be accomplished by utilizing upstreamsetting means, i.e., by employing plasticizing agents (e.g., heat orsolvent) upstream from the twister so that the yarn is twisted while inthe plastic or semi-plastic state. Upon passing such setting means, theyarn becomes set in the twisted configuration. Twistsetting also occurson the beam when a dry-spun yarn (e.g., cellulose acetate) containingresidual solvent is packaged, since such a yarn is twisted while in thesemi-plastic state. Eventual evaporation of the residual solvent leadsto twist setting. Twist which has been set may be relieved by increasingthe yarn tension during backwinding. Twist may be releasably held byslashing.

Many species of mechanical or pneumatic twisters may be employed incarrying out the process of this invention. For example, in FIGURES l0and 11 are shown variations of the pneumatic twister of FIGURE 2 whichare useful in the warp twisting applications. In FIGURE is shown thetwister 8 having twisting section 18 and fluid conduit 19 as in FIGURE2. A yarn string-up slot 33 is out throughout the length of the twister8. In operation, air entering through conduit 19 serves to screen thestring-up slot, so that the twister operates at full efliciency. Thistwister is ideally suited for spin-beaming where rapid string-up andcontinuous operation are prerequisites. In FIGURE 11 is shown thetwister 8 having twisting section 18, fluid conduit 19, and theadditional fluid conduit 34. In operation, air enters the twister 8alternately through fluid conduit 19 and fluid conduit 34. Operation issimilar to that of the mechanical twister in Example 2, i.e., resemblesintermittent unidirectional twisting through one-half of the twistingcycle; during completion of the cycle, fluid enters the twister throughthe opposite fluid conduit, thereby positively applying twist of theopposite direction onto the yarn being packaged. The twister of FIGURE11 has an additional advantage, namely, that twisting in any givendirection may be carried out for longer times before the initiation ofan equilibrium twisting condition. Fluid supply may be provided to thetwister of FIGURE 11 by use of rotary valve means, or by suitablemodification of the apparatus of FIGURES 55a.

The process of this invention is applicable to any continuousmultifilament yarn, such as poly(hexarnethylene adipamide),poly(e-caprolactam), or other polyamides, polyesters, such aspoly(ethylene terephthalate), poly- (acrylonitrile), or its copolymers,and other polyacrylates, regenerated cellulose (rayon) or protein,cellulose acetate, poly(vinyl chloride or acetate), poly(vinylidenecyanide or chloride), any suitable copolymers of the foregoingmaterials, glass and many other fiber-forming compositions. Yarnprepared from such compositions may contain 2 or more filaments per yarnbundle, and the total denier of such a yarn bundle may range upwards toseveral thousand or more grams. When warp twisting extremely large orsmall yarn bundles, twister dimensions may be adjusted for optimumtwisting. Such yarns may contain any of the usual textile additives,e.g., titanium dioxide as a delustrant or copper chloride/ potassiumiodide as an anti-oxidant, and may be finished in accordance withaccepted practice.

The process of this invention is applicable to any packaging operation,but it is most useful in those cases where two or more yarn ends aresimultaneously wound onto a common package core. Difiiculties inbackwinding zerotwist yarn become most pronounced whenever such yarn iswound at reduced hel x angles; hence in lieu of either true twisting orslashing, the practice of this invention becomes an essentialprerequisite to good backwindability whenever several yarn ends arewound at such reduced helix angles. Of course, the mternate twist in thepackaged yarn may be regular or irregular with respect to twist periodand average level, so long as the average level does not fall belowabout 0.4 t.p.i., and may contain reasonable lengths of zero-twist yarnat the reversal points. It is noted that the yarn cross section becomescircular as the twist level increases, and individual filaments in theyarn bundle tend to spread into a band or ribbon at segments of zerotwist. Accordingly, at close yarn-to-yarn spacings in the warp, thelength of such zerotwist yarn segments, relative to the length of thetwisted segments, should be minimized.

The practice of the present invention is of obvious advantage in thevarious handling operations of continuous multifilament zero-twist yarn,particularly for the replacement of the discontinuous operation of truetwisting yari s prior to beaming. The beam prepared by this invention isbackwindable with or without twist removal, and the formation offilament ringers is avoided. In accordance with a preferred embodimentutilizing pneumatic twisting, beaming may be carried out rapidly(200-600 y.p.m. or more) and continuously with a minimum of addedinvestment or operating costs. Yarn quality is undirninished. Furtheradvantages inherent in the practice of this invention will readily occurto those undertaking its practice. Pneumatic false twisting apparatusand methods which may be used are disclosed in application Serial No.598,135, filed July 16, 1956, by Breen and Sussrnan, now US. Patent No.3,009,309.

The claimed invention:

1. A Warp beam wound with a warp sheet of a large number of essentiallyparallel continuous multifilarnent yarn ends under tension, having ayarn-to-yarn spacing of less than about one-half inch between theindividual yarn ends in the warp winding, each of said individual yarnsconsisting of a single bundle of filaments having maintained thereinsolely by being trapped on the beam from about 0.4 to about 0.8 averageturn per inch of releasable alternating twist at a period length of fromabout 4 to about 16 feet as the essential means for maintainingsufficient unity of the filament bundle to provide a beam whichbackwinds without entangling of filaments and without the formation offilament ringers, the beam being backwindable into a warp withsubstantially complete removal of the alternating twist by merelyproviding a free suspended length greater than said period length.

2. A backwindable beam as defined in claim 1 wherein the separate yarnends have substantially zero net twist therein.

3. A beam as defined in claim 2 which backwinds to supply a warp ofcontinuous multifilament yarn wherein the separate yarn ends havesubstantially zero twist.

4. A backwindable beam as defined in claim 1 wherein the alternatingtwist in the individual yarns is out of phase with that of adjacentyarns so that twist reversal points are separated by twisted portions ofintermediate yarns 2,702,982 Guyot Mar. 1, 1955 across the warp winding.2,741,893 Vandamme et a1; Apr. 17, 1956 5. A baekwinda'ole beam asdefined'in claim 1 wherein 2,751,747 Burleson June 26, 1956 thereis lessthw one-half inch of traverse in the wound 2,778,187- Leath et all Ian.22, 1957 yam, 5 2,813,393 Kingsburg et a1. Nov. 19, 1957 6. Abackwindable beam as defined in claim, 1 wherein 2,846,839, Billion Aug.12, 1958' the yarn is tire yarn having aboutt0.6 turn per inch of2,846,840 Billion AugQ12, I958 releasable alternating twist at a periodlength of about 2,863,280 Ubbelohde Dec. 9, 1958 6 feet to provide anefiective supply beamfor multi-end 2,909,028 Comer et a1. Oct.'2(), 19592 true twisting into uniformlytwisted tire cord. I 10 2,952,116 BurlesonSept. 13, 1960 References Cited in the file of this patent FOREIFHTIPATENTS UNITED STATES PATENTS 355,447 Great Brrtam Aug. 27, 1931'2,370,899 Wildbore Mar. 6, 1945 i

